An Indian Border Security Force (BSF) soldier reacts as his colleagues apply coloured powder on his face during Holi celebrationsDanish Ismail/Reuters

A group of Pakistani-based militant operatives led by a former soldier entered neighbouring India, purportedly to carry out terror attacks when the country celebrates Holi, the festival of colours. The Indian intelligence agency has issued an alert in several states including the capital, New Delhi.

Besides the Delhi police, about 2,500 paramilitary troops have been deployed across Delhi as part of the heightened security measures. Hotels and hospitals have been sent warnings by the security agencies.

"The intention of this group is to kill citizens in Delhi in hotels and hospitals on or before Holi," says an alert message sent by India's top spy agency Intelligence Bureau (IB). Security agencies in the states of Punjab and Assam were specifically asked to remain vigilant.

At least six militants have accompanied the suspected Pakistani soldier — named Mohammad Khurshid Alam alias Jahangir — when he sneaked into the country through the northern border state of Punjab. According to the intelligence sources cited by local media, Alam had earlier visited the country spending several days there.

"Every precautionary measure is being taken and elaborate arrangements have been made," said Arvind Deep, special commissioner of Police (Special Cell) in Delhi. The alert has been issued via the multi-agency centre (MAC) — a mechanism by which all the law enforcement agencies receive the threat warnings. The MAC was put in place after the 26/11 Mumbai attacks.

The warning has come on the heels of the recent Pathankot attack. In January 2016, a heavily armed militant group attacked the key Indian air base in Punjab. The operation was led by four militants, who were killed after a lengthy stand-off with security personnel.